(3R,4S)-3,4-Isopropylidenedioxy-3,4-dihydro-2H-pyrrole 1-oxide

The title compound C7H11NO3 was prepared by intramolecular nucleophilic displacement of 2,3-O-iso-propylidene-d-erythronolactol. There are two molecules in the asymmetric unit, which are related by a pseudo-inversion centre. The crystal structure determination confirms unequivocally the configuration of the chiral centres as 3S,4R. In the crystal structure, intermolecular C—H⋯O interactions link the molecules (into infinite zigzag chains along the a axis.

The title compound C 7 H 11 NO 3 was prepared by intramolecular nucleophilic displacement of 2,3-O-iso-propylidene-d-erythronolactol. There are two molecules in the asymmetric unit, which are related by a pseudo-inversion centre. The crystal structure determination confirms unequivocally the configuration of the chiral centres as 3S,4R. In the crystal structure, intermolecular C-HÁ Á ÁO interactions link the molecules (into infinite zigzag chains along the a axis.

Comment
Nitrones have been the subject of intense research efforts, because of the wide role played in the synthesis of complex molecular frameworks. They undergo several synthetically useful reactions such as 1,3-dipolar cycloadditions, (Tufariello et al., 1984) nucleophilic additions, (Merino et al., 2000;Lombardo et al., 2002). Both the reactions give rise to the formation of new carbon-carbon bonds, often with a high degree of stereocontrol. These features, together with the direct access to nitrones by simple reactions (Hamer et al., 1964;Döpp et al., 1990), and their stability which permits isolation and long storage, make nitrones ideal tools for application in organic syntheses, particularly in the field of alkaloids, nitrogen containing natural products or bioactive analogues. The construction of highly functionalized nitrogen heterocycles in a stereoselective manner is an important focus of medicinal and natural product chemistry. Although, in the last few years, the title compound has been reported more and more in the literature as a starting material due to its biological relevance in the synthesis of polyhydroxypyrrolidines or polyhydroxypyrrolizidines, both interesting compounds as potential glycosidase inhibitors and consequently as potential therapeutic (antibiotic, antiviral, antitumoral) agents (Hall et al., 1997;Closa et al., 1998;McCaig et al., 1998;Cicchi et al., 2002;Revuelta et al., 2007) there was not any crystallographic data.
Following our special interest in nitrogen compounds such as isoxazolidines, we prepared the title N-oxide, and its crystal structure is reported here.
The asymmetric unit contains two symmetrically independent molecules. The title molecule consists of a pyrroline-Noxide ring with an isopropylidenedioxy as substituent. All the bond lengths and angles are within the normal ranges. The carbonyl group at N1 is coplanar with the pyrroline ring being the O3-N1=C3-C4 and O3'-N1'=C3'-C4' torsion angles of 179.1 (4)° and 179.2 (7)°, respectively. These results are in good agreement with the literature (Keleşoğlu et al., 2010).
In the crystal structure, intermolecular C-H···O interactions (Table 1)

Experimental
The title N-oxide was obtained by intramolecular nucleophilic displacement, which is based on a simple one-pot procedure employing NH 2 OSiMe 2 t-Bu, methanesulfonyl chloride, and 2,3-O-iso-propylidene-D-erythronolactol, according to the methodology described by Cicchi et al. (2006) and by us (Flores et al., 2010). Well shaped colourless single crystals were obtained by crystallization from CH 2 Cl 2 /MeOH.